| 摘要 |
Apparatus for driving a surfboard comprising an internal combustion engine mounted on a box on rear portion of the surfboard and a water jet propelling device driven by the internal combustion engine for propelling the surfboard. The exhaust gas system and the water jet propelling device are provided in the box. A part of the jet water is used as a cooling water of the engine. The box comprises three superimposed cases having partitions, dividing the box into an exhaust gas passageway constituting a plurality of expansion chambers and passages for exhaust gases with the exhaust gas passageway defining a gas exhaust path arranged in three dimensions, thereby preventing entry of water from the outlet port through the exhaust gas passageway to the exhaust port of the engine. |
